Preparation of magnetic, luminescent and mesoporous hydroxyapatite nanospindles with high specific surface area

Magnetic, luminescent and mesoporous nanospindles of Sm³⁺-Fe³⁺ co-doped hydroxyapatite (HAP) were prepared in the presence of monododecyl phosphate as templates. X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), vibration sample magnetometer (VMS), photoluminescence (PL) spectrum and nitrogen adsorption-desorption isotherm were used to characterize the products. The results show that the doped Sm³⁺ and Fe³⁺ existed in two forms: being solid-soluted in the HAP, or as oxides (amorphous Sm₂O₃ and γ-Fe₂O₃) nanoparticles embedded in the HAP. The doped HAP samples, both the as-dried and the calcined, display a good superparamagnetism. The calcination increases the magnetization from 13.45 emu/g to 19.51 emu/g. The calcined Sm³⁺-Fe³⁺ co-doped HAP has a spindle-like morphology with a length of 200~350 nm and a diameter of 50~100 nm, and possesses a large amount of mesopores with biomodal pore sizes of 3.64 and 9.01 nm. The biomodal mesoporous Sm³⁺-Fe³⁺ co-doped HAP nanospindles have a large pore volume of 0.3286 cm³/g and a high specific surface area of 153.52 m²/g. These make the mesoporous HAP nanospindles have a high drug payload ratio of 33.68wt% and a great application potential in drug delivery system.